Module development and code questions

I have spent a great deal of time researching and I seem to be finding conflicting ideas. I think part of it is a mix of articles talking about drupal 6, 7, and 8. What I am looking for is direction and possibly a simple example. I am going to try and simplify my goal so hopefully some kind soul can help provide a roadmap or small example module.

Simplest Scenario

in Drupal, some dynamic content can be achieved either by cache or lazy builder, 
can some one help to make it clear, in what situations, to apply one of the two means?

thanks.

from time to time, we can see snippet using #cache key, say

  '#cache' => array(
    'keys' => ['ascii-art', 'llama'],
    'tags' => ['node','node_list'],
    'context' => ['session','user.permission'],
    'max-age' => 3600,
  ),

can some one help us to make it clear, when caching, which one [keys, tags, context, max-age] do the drupal core to respect and handle?
is there any conflict or privilege among them?

thanks very much.

Hi ,

isSyncing() method seems to be only available for config entities.

Does it exist for content entities ?

Thx

Hey guys,

I just wanted to know if there is anyway we can integrate the LibCal widget to our website. Is there any module that can do that?

Thanks.

Hi all,

I am going crazy over my implementation of hook_node_grants() and hook_node_access_records(). I set up a few custom grants and everything is working fine - as long as I am only viewing nodes my grants are beeing respected.